1. Field of the Invention
The present invention relates to improvements in adjustable flow control clamps. More particularly, the invention relates to improvements particularly suited for controlling water flow in flexible plastic irrigation pipes commonly referred to as layflat polypipe. In particular, the present invention relates specifically to a flow control valve for use on gradients or downslopes to control the flow rate and limit head pressure on the layflat polypipe.
2. Description of the Known Art
Layflat polypipe is a flexible lay flat tubing sold in long rolls used for irrigation with low pressure water movement on relatively flat surfaces. Layflat polypipe is manufactured in 6 mil to 15 mil thickness from polyethylene with a diameter of 6 to 22 inches and in lengths up to 1320 ft spirally wound on central core tubes. The pipe is laid into a flat bottom furrow generally dug by a tractor along the ends of the furrows in a crop field. Dirt is thrown on top of the pipe every 10 to 15 feet to hold the pipe in place until it is filled with water. Because the size of the pipe is controlled by the amount of water needed to be carried to the crops; the amount of water to flow through the pipe is determined by the crop being grown and the weather; and the length of the pipe is controlled by the size of the field to be irrigated, the grower does not have much control over the input costs associated with purchasing the pipe. In contrast to these uncontrolled variables, the pipe is sold by the pound such that by buying a thinner pipe, less money needs to be expended by the user. This creates a problem because the thin 6 mil to 15 mil thickness means that the layflat poly pipe can only handle a water head of less than one to three feet and/or less than 1.5 Psi or even 0.6 Psi on the thinnest pipes. This means that the field must be substantially flat, or something needs to be done to control the flow through the pipe and the head pressure. On slight gradients, the flow and head pressure can be controlled with dirt mounds built up under the pipe or by laying ½ barrels under the pipe when the pipe is installed to build up small pools inside the pipe to slow the water flow. Thus, when a gradient is encountered, dirt may be piled up under the pipe to create a small dam that pools the water in the pipe to limit the down pipe head pressure. This solution has problems in that the dirt piles are not uniform sizes, the dirt piles erode over time, and the layflat pipe may shift off of the dirt pile. Downhead pressure is also controlled by the number of outlets cut into the pipe. The layflat polypipe is typically placed perpendicular to the furrows and small holes are punched/cut into the top and upper sides of the polypipe to let the appropriate amount of water out of the pipe to control the amount of water supplied in any particular area. If too much water is released at or toward the distal end of the pipe, the pipe never fills and water does not reach the height of the middle holes to allow for water release along the length of the pipe. Thus, the system must be balanced for flow and pressure within the limits of the layflat polypipe. These and other problems exist in the known art.
As will be appreciated by those skilled in the art, valves and clamps are known in various forms. Patents disclosing information relevant to valves and clamps include: U.S. Pat. No. 2,693,203, issued to Hempel on Nov. 2, 1954; U.S. Pat. No. 3,942,228, issued to Buckman, et al. on Mar. 9, 1976; U.S. Pat. No. 3,960,149, issued to Bujan on Jun. 1, 1976; U.S. Pat. No. 4,063,336, issued to Jones, et al. on Dec. 20, 1977; U.S. Pat. No. 4,190,232, issued to Clements on Feb. 26, 1980; and U.S. Pat. No. 4,588,160, issued to Flynn, et al. on May 13, 1986. Each of these patents is hereby expressly incorporated by reference in their entirety.
From these prior references it may be seen that these prior art patents are very limited in their teaching and utilization, and an improved polypipe valve is needed to overcome these limitations.